BVP - Strabismus Assessment II - Week 11

Question 1

How can the comitancy of strabismus be checked?

Answer 1

Observe the magnitude of the strabismus in all 9 gazes using a pentorch (hirschberg) or cover test

Question 2

What is meant by a comitant strabismus?

Answer 2

It has the same magnitude in all 9 directions of gaze

Question 3

What is meant by a incomitant strabismus?

Answer 3

Varies by 10^D or more in different positions of gaze

Question 4

Describe what incomitancy would be seen with a 4th nerve palsy (what strabismus and in what gaze).

Answer 4

Vertical incomitance in R-L gaze

Question 5

Describe what incomitancy would be seen with a 6th nerve palsy (what strabismus and in what gaze).

Answer 5

Horizontal incomitance in R-L gaze.

Question 6

Describe what incomitancy would be seen with musclew malinsertion (what strabismus and in what gaze).

Answer 6

Horizontal incomitance in up-down gaze

Question 7

Describe what incomitancy would be seen with a high AC/A ratio (what strabismus and in what gaze).

Answer 7

Horizontal incomitance in near-far fixation

Question 8

List three common causes of incomitancies.

Answer 8

A and V pattern in esotropia and exotropia
4th nerve palsy
Duane’s syndrome

Question 9

What is the cause of duane’s syndrome?

Answer 9

Congenital 6th nerve palsy

Question 10

What is the cause of 4th nerve palsy (2)?

Answer 10

Can be congenital but also trauma

Question 11

What does A and V pattern in esotropia and exotropia indicate and what prognosis (good or poor)?

Answer 11

Indicates early onset strabismus with poor prognosis

Question 12

List 3 uncommon causes of incomitancies. Note if it is acquired or congenital.

Answer 12

Browns syndrome
Acquired 6th nerve palsy
Congenital 3rd nerve palsy

Question 13

What is browns syndrome and what happens with time?

Answer 13

Problem relaxing the superior oblique through the trochlea that often improves with age

Question 14

Consider a monocular H test (action field). List the muscles used to bring the eye to each fixation (one each) for all 6 positions.

Answer 14

IO         SR
  I            I
MR ----- LR
  I            I
SO         IR

Question 15

Describe the parks three steps test (3).

Answer 15

Note which eye is higher (hypertropic) in the primary gaze
Note if the hypertropia is worst in the left or right gaze
Note if the hypertropia is worst if the head is tilted left or right, using the midline of the head to note affected muscles
In each case, using a monocular H action field circle the affected muscles
By the end of the test, the muscle circles most (three times) is the affected muscle
-note which eye and muscle

Question 16

List the three golden rules of pratt johnson.

Answer 16

The strabismus is a superior oblique palsy until proven otherwise
Congenital until proven otherwise
Patients usually dont fixate with the eye that has a palsy

Question 17

What is the deviation of esotropia like at near vs distance typically?

Answer 17

Often the same

Question 18

Describe what convergence excess esotropia is, its cause, and what it responds to.

Answer 18

When near deviation of esotropia is worse than distance
Almost always caused by a high AC/A ratio
Responds to plus addition (bifocals)

Question 19

What is it called when distance deviation of esotropia is worse than near deviation?

Answer 19

Divergence insufficiency

Question 20

What is divergence deficiency usually caused by?

Answer 20

6th nerve palsy, which innervates the lateral rectus - abduction deficit

Question 21

What is 6th nerve palsy typically caused by (pathology)? What should be done in these cases?

Answer 21

Intracranial pathology that increases pressure inside the brain (hydrocephalus or tumour)

Urgent referral to an ophthalmologist needed, may have papilloedema